1. Field of the Invention
The present invention relates to an image display apparatus for displaying an image by displaying a plurality of pixels, each having a luminance distribution.
2. Description of the Prior Art
As an image display apparatus, there is provided an image display apparatus in which a light from a light source is applied to a liquid crystal panel having pixel openings corresponding to a plurality of pixels and a light transmittance is controlled for each of the pixel openings. In this type of image display apparatus, there is a target to increase luminance of each pixel so as to display a clear and bright image, Furthermore, in order to display a color image in this type of image display apparatus, normally, color filters corresponding to the three primary colors are arranged corresponding to each of the pixels However, the color filters bring about a problem to decrease the luminance. Therefore, the image display apparatus capable of displaying a color image has a great problem to increase the pixel luminance.
To cope with this, as an image display apparatus capable of obtaining a high luminance in color image display, there has been proposed an image display apparatus 101 as shown in FIG. 1. This image display apparatus 101 includes: a light source 102 which emits a white light; a dichroic mirror 103 which reflects the light from the light source 102, into three primary colors; a display device 104 having pixel openings corresponding to pixels; a projection lens 105 for projecting an image; and a screen 106 for displaying an image projected by the projection lens 105.
In this image display apparatus, the light from the light source 102 is separated by the dichroic mirror 103 into three primary colors of red, green, and blue colors, which are introduced into the display device 104 as different incident angles, respectively. The display device 104 has a liquid crystal panel having pixel openings corresponding to the pixels constituting an image, and a micro array lens consisting of a plurality of lenses, each corresponding to three pixel openings on the liquid crystal panel. The red, green, and blue lights from the dichroic mirror 3 is respectively focused by the micro array lens in different pixel openings. That is, in this image display apparatus 101, utilizing the difference in the incident angle of the red, green, and blue lights into the display device 104, the red, green, and blue lights are respectively focused by the micro array lens in the different pixel openings. Thus, without using color filters, it is possible to obtain pixels for displaying the red color, pixels for displaying the green color, and pixels for displaying the blue color. Moreover, the liquid crystal panel controls the light transmitting state for each of the pixel openings so as to obtain a desired image. Thus, it is possible to obtain a color image consisting of the red, green, and blue pixels. The image obtained is projected by the projection lens 105 onto the screen 106. In this image display apparatus 101, the light itself is introduced as red, green, and blue lights to the pixels and accordingly no color filters causing luminance lowering are required. Consequently, it is possible to obtain a color image with a high luminance.
However, in the aforementioned image display apparatus, the light introduced to each of the pixel opening is focused by the lens and it is impossible to obtain a uniform distribution of luminance within a pixel. Moreover, the size of the pixel itself displayed is normally defined as smaller than the pixel opening formed on the liquid crystal panel.
FIG. 2 shows such a pixel display state in the image display apparatus. It should be noted that in FIG. 2, the pixel opening is indicated by a dotted line and a pixel actually displayed is indicated by a solid line. As shown in FIG. 2, the actually displayed pixel is a circular spot smaller than the rectangular pixel opening. For this, when a large screen image is to be obtained, a vacancy between pixels called black stripe becomes noticeable. Such a black stripe forms a meshwork pattern on the displayed image. It is preferable to make the black stripe less noticeable. Moreover, in this image display apparatus, as each pixel is displayed as a circular sport smaller than the pixel opening, the image displayed is deteriorated by the prominent black dots of the meshwork.
Furthermore, in the image display apparatus capable of displaying a color image, a set of pixels corresponding to the three primary colors is arranged with a predetermined repetition cycle. If an interval between pixels is large, the repetition of pixels of an identical color becomes prominent and the image displayed is greatly deteriorated. Moreover, as shown in FIG. 3, in a case when the red pixel openings R, blue pixel openings B, and green pixel openings G are arranged in the so-called checker pattern, the interval between identical color pixels is increased in the diagonal directions, causing unevenness in the image displayed.
In order to solve these problems in the image display apparatus, it is required to reduce the pixel interval and increase the number of pixels. However, it is not easy to realize this, considering the production yield and production costs.
By the way, in a pickup apparatus such as a CCD camera, it is possible that an image signal picked-up can be subjected to an electrical processing so as to make the vacancy between pixels less noticeable. That is, in a pickup apparatus such as a CCD camera, it is easy to apply an electric processing by way of low-pass filtering to the image signal pickup-up, so as to make the interval between pixels less noticeable. Thus, in the pickup apparatus, the image signal picked-up is subjected to an electric processing, so as to suppress deterioration of the image caused by the interval between pixels and the like.
On the other hand, in the image display apparatus, in order to make the vacancy between pixels less noticeable, it is necessary to fill the vacancy after the light is emitted from the display device. Consequently, it is difficult to carry out an electric processing so as to make less noticeable the meshwork pattern formed by the vacancy between the pixels and the repetition cycle of identical color pixels. That is, in the image display apparatus, it is necessary to employ an optical processing instead of electrical processing, for making less noticeable the vacancy between the pixels.
As an optical processing in the image display apparatus for making less noticeable the vacancy between the pixels, there can be exemplified a method for blurring the lens focus for the viewers. However, in this method, the image to be displayed itself is blurred and it is not preferable to apply such a method. Moreover, in the aforementioned image display apparatus in which the red, blue, and green light are introduced to the display device at different angles so as to eliminate use of the color filters, if the lens focus is blurred, the red, blue, and green pixel positions are displaced, causing mismatching between the three primary colors. Consequently, in this image display apparatus, it is impossible to employ the method of lens focus blurring for making less noticeable the vacancy between the pixels. Moreover, there is also a so-called non-glare method which uses an obscured glass or the like so as to diffuse the pixels, but this method makes the screen obscure and it not so preferable.